This section provides background information related to the present disclosure which is not necessarily prior art.
For example, as shown in FIG. 6, in the matter of gasket 51 comprising the seal in the stack in the solid polymer fuel cell, a multiplicity of embodiments have been invented, wherein the seal was formed from a one-piece mold on the plate-shape attachment part (hereinafter, also merely termed plate) 52 such as separators and MEA (membrane electrode assemblies). (For example, see Patent Reference 1.) For these one-piece molded gaskets 51, space-saving designs are required so that the power generation area 53 on plate 52 can be as broad as possible.
Further, a method has also been proposed, wherein a pair of gaskets 51 is molded at one time on both faces of plate 52, by providing a through-hole at the position directly on top of gasket 51 and the flat face in plate 52 for separators and MEA and the like. For example, in the case of MEA, a pair of gaskets 51 is molded in one piece on the anode side and the cathode side, in the case of separator, on the anode side and the cathode side, on the anode side and the cooling face, on the cathode side and the cooling face.
However, when these through-holes are provided directly under the seal lip, this is not suitable, because shrinkage of gasket 51 from vulcanization, for example, occurs, and adequate surface pressure and reactive force are not obtained. Consequently, as shown in FIG. 7, the through-hole 54 is provided in a section distant from being directly under seal lip 55. In other words, since gasket 51 has as one unit, seal lip 55, extending in the lengthwise direction of the gasket, and side section 56, located on both sides or on one side (both sides in the figure) of seal lip 55 and lower in height to seal lip 55, the through-hole 54 is provided at the position directly on top of the flat face and the side section 56 of the latter. However, in this case, because space is necessary for molding gasket 51 on the through-hole 54 part, when the seal groove for gasket 51 is provided on the partner part for gasket 51 (the part that is face to face with gasket 51 when the stack is tightened, not shown in the figure), the shape must be designed in such a way that the through-hole part 54 fits in the groove. In other words, even when the width w1 of gasket 51 and the width of the groove in which this fits are designed to be at a minimum, the gasket width w2 and the groove width become large in the through-hole 54 part. As a result, it is not possible to respond to the aforementioned space-saving requirements.
Further, in order to solve this problem, it is conceivable to make the through-hole 54 smaller. In other words, the conventional opening shape of the through-hole 54 is circular (true round shape), so it is conceivable that the diameter can be made smaller. Nevertheless, when through-hole 54 is made smaller in this way, the molding material cannot fill the entirety of the opposite face (toward the gate side) of plate 52 by one-time injection molding. It is believed that there are contributing effects of pressure loss and such at the time of passage of the molding material through the through-hole 54. Furthermore, when the input gate for the molding material for the metal mold (injection gate for rubber molding) is located on the flat face directly on top of the small through-hole 54, there is concern for deformation of the through-hole 54 part on plate 52 from the effects of the injection pressure.
Patent Reference 1: Japanese Patent Disclosure, Kokai 2005-166508A